Aurichalcite
| Aurichalcite | |
|---|---|
|
Aurichalcite, 79 Mine, Banner District, Gila County, Arizona, USA | |
| General | |
| Category | Carbonate mineral |
| Formula (repeating unit) | (Zn,Cu)5[(OH)3|CO3]2 |
| Strunz classification | 05.BA.15 |
| Crystal symmetry | Monoclinic 2/m |
| Unit cell | a = 13.82 Å, b = 6.419 Å, c = 5.29 Å; β = 101.04°; Z=2 |
| Identification | |
| Color | Pale green, greenish blue, sky-blue; colorless to pale blue, pale green in transmitted light |
| Crystal habit | Typically in tufted divergent sprays or spherical aggregates, may be in thick crusts; rarely columnar, laminated or granular |
| Crystal system | Monoclinic-prismatic |
| Twinning | Observed in X-ray patterns |
| Cleavage | {010} and {100} Perfect |
| Fracture | Uneven |
| Mohs scale hardness | 2 |
| Luster | Pearly, silky |
| Streak | Light blue |
| Diaphaneity | Transparent |
| Specific gravity | 3.96 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.655 nβ = 1.740 nγ = 1.744 |
| Birefringence | 0.0890 |
| Pleochroism | Weak colorless to pale green |
| 2V angle | Measured: 1° to 4°, Calculated: 22° |
| References | [1][2][3] |
Aurichalcite is a carbonate mineral, usually found as a secondary mineral in copper and zinc deposits. Its chemical formula is (Zn,Cu)5(CO3)2(OH)6. The zinc to copper ratio is about 5:4.[2]
Occurrence
Aurichalcite typically occurs in the oxidized zone of copper and zinc deposits. Associated minerals include: rosasite, smithsonite, hemimorphite, hydrozincite, malachite and azurite.[1]
It was first described in 1839 by Bottger who named the mineral for its zinc and copper content after the Greek όρειχαλκος, for "mountain brass" or "mountain copper", the name of a fabulous metal. The type locality is the Loktevskoye Mine, Upper Loktevka River, Rudnyi Altai, Altaiskii Krai, Western Siberia, Russia.[2]
References
Display at the Arizona-Sonora Desert Museum
Aurichalcite in gossan
Needle Crystals of Aurichalcite from Nevada, USA
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